1. Field of the Invention
The present invention relates to an elevator for press rolls disposed in a heating part or the like of a double facer in a corrugate machine.
1. Description of Background Art
In a heretofore known double facer of the above-described type, as shown in FIG. 4(A), a single-faced corrugated cardboard sheet a having starch applied to its flute tips by means of a glue machine 1 (See FIG. 5) and a liner b which is preliminarily heated by a preheater 2 (See FIG. 5) enter the machine and are laminated. In a heating part 10A sheets a and b are conveyed and pinched between a heating box 4 on the lower side and a canvas belt 3 on the upper side (3a denoting a drive pulley). In a cooling part 10b, they are conveyed and pinched between the canvas belt 3 on the upper side and a conveyor belt 5 stretched between pulleys 5a and 5b. Pressing forces are applied to sheets a and b from the upper side via the canvas belt 3 by a large number of press rolls 9 which are disposed as spaced in the direction of travel and cause the sheets and ascend and descend. In the heating part 10a, the heat from heating boxes 4 cause the starch to gel resulting in a bonded and joined double-faced corrugated cardboard sheet a, b. After the corrugated cardboard sheet has cooled and regulated in nature (correction of warp deformation or the like) in the cooling part 10b, it travels to the next step of the process.
As further illustrated in FIG. 4(B), press rolls 9 are rotatably supported between connecting shafts 25 via bearings 23a, connecting shafts 25 are supported by air cylinders 21 at the top of the both side frames 10 of the double facer by the intermediary of yokes 22, pins 23 and bearings 24, thereby there is provided a press roll elevator in which the press rolls 9 are elevated and lowered. The corrugated cardboard sheets are pressed via the canvas belt 3 by the respective press roll 9 disposed at an interval in the traveling direction of the sheets. The pressing forces are useful for promoting the heating in the heating part 10a and also for facilitating conveying the sheet by increasing a frictional force between the canvas belt 3 and the corrugated cardboard sheet. It is necessary to set an appropriate pressing force such that it does not crush the flute tips, and with regard to the strength required for the pressing force, it is necessary to make the strength adapted to the conditions such as a manufacturing speed of the double-faced corrugated cardboard sheet a, b (a sheet traveling velocity), specifications (material and paper sheet thickness) of the raw material paper sheets for the corrugated cardboard sheet, types and combinations of flutes of the corrugated cardboard sheet, working environment (room temperature or the like).
The above-described press roll elevator shown in FIGS. 4(A) and 4(B) is constructed to elevate press rolls 9 by feeding pressurized air into a pair of air cylinders 21 provided for each press roll 9 thereby making the press roll inactive. On the other hand, the air cylinders 21 are made to be inactive for allowing the rolls 9 to descend due to their own weight and thereby applying the above-mentioned pressing force. A characteristic feature of the elevator is that a number of operative press rolls 9 can be selectively preset for adjusting over-drying or insufficient heating of the sheet which varies depending upon various conditions such as specifications of the sheet, machine speeds and the like.
In a further embodiment shown in FIGS. 5(A) and 5(B), press rolls are rotatably supported in a heating part 10a between top end portions of respective pairs of arms 12 which are pivotably supported from the both side frames 10. The press rolls 9 are disposed at an interval in the traveling direction of the sheet, and respective protrusions 16 on rails 15 which are reciprocated along the traveling direction of the sheet are held in contact with the lower portions of the respective arms 12 to swing the arms 12. Rails 15 are reciprocated by means of geared motors or the like via wheels, screw shafts 17, and the like, hence the respective press rolls 9 are synchronously raised as a whole by the reciprocating motion of the respective rails 15 and descend due to their own weights thereby applying pressing forces to the sheet. In addition, cooling part 10b includes respective arms which are disposed so as to be swingable about fulcrum shafts on both side frames 10 and the respective press rolls attached to the ends of the arms are actuated to ascend and descend through a mechanism similar to that described above. Further, the thicknesses of the single-faced corrugated cardboard sheet a and the liner b are detected in cooling part 10b which produces a detection signal representative thereof. The above-described rails 15 are controlled in response to that detection signal, thus the pressing forces of the respective press rolls 9 are adjusted as a whole, and the gap distance between the canvas belt 3 and the heating box 4 can be appropriately adjusted depending upon the thickness of the corrugated cardboard sheet.
In the prior art example shown in FIGS. 4(A) and 4(B), the adjustment for individually elevating and lowering the respective press rolls while holding them in parallel to the top surface of the heating box is difficult because the both ends of the respective press rolls are elevated and lowered by actuating the respective air cylinders. In some cases, the press rolls would descend at an inclined state and would partly crush the flute tips of the corrugated cardboard sheet. As a counter-measure for preventing such accident, it is necessary to additionally provide a sheet flute crush preventing device, such as stoppers for the press rolls, which can be adjusted in correspondence to the thickness or the like of the corrugated cardboard sheet. Also, a large number of air cylinders and electromagnetic valves for control purpose are necessitated, which increases the likelihood of troubles such as seizure of a coil in the electromagnetic valve or faulty operations caused by dust or the like entered into the piping. Furthermore, pneumatic machines such as compressors or the like and various relevant equipment such as air pipings or the like become necessary resulting in a more complicated and expensive structure.
In the example of the prior art shown in FIG. 5, since the respective arms for supporting the respective press rolls are disposed on the upper side as well as on the lower side of the corrugated cardboard sheet, and also since the respective arms and the respective press rolls are synchronously elevated and lowered as a whole at the same time, it is impossible to adjustably control the pressing forces in correspondence to the conditions (traveling speed, sheet thickness, etc.) of the corrugated cardboard sheet. Also, difficulties would accompany the work of removing starch dregs sticking to the upper surface of the heating box and cleaning the surface, and so, there exists the problem that the work takes too much time and the rate of operation (productivity) of the machine is lowered.